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Depends what you call 'expensive'.
£200-£300 for a 2nd hand scope may look expensive compared to £20 for a new DVD player. These are professional scopes which are extremely well built and rugged
Don't forget about probes! - you're wasting your money if you buy a 500Mhz scope and then use 10Mhz probes.
If you do want to buy a scope then move quick - there will be lots of people looking for scopes at the start of term.
I bought a useful scope from a radio rally several years ago.
It is only low spec but was very cheap (I think it was about £30) and is good enough to check most waveforms that I need to (using microcontrollers etc).
Unfortunately, radio rallies are in decline in my area and I stopped going to them a few years ago because of this.
I notice there is what looks to be a good one in your area (Kent) at the end of August: http://www.military-odyssey.com/
Be wary though, there is some real junk sold at rallies just like on ebay, but if you are lucky you may find some interesting stuff.
Looking again at the web page, It appears to be more a military collectibles market rather than radio rally.
I found it listed on a rally page though? http://home.freeuk.com/g4rga/08Aug.html
The question of the sampling rate came up and the discrepency is in the fact that usually, the more channels in use, the lower the sampling rate and the specs presented defy that logic.
Stand alone scopes, for instance Tektronix's lowest-priced scopes, typically have a 2GS/s rate, 26 times faster than the 75MS/s spec.
As mentioned, true stand-alone scopes of lab quality and in good condition can be had for good prices, usually for far less than 1/10 of what they originally sold for. They are worth the money.
And don't get caught up in the logic that a digital scope is the only way to go. A good analog scope will outperform a low-end digital scope. The only thing the digital scope will offer is cheap storage, something that we techs have lived without all these years with no problems.
If what you want to do is check slow analog signals (less than 60MHz) and limit square waves (digital signals, like a processor clock) to 6MHz, an don't mind being being chained to a PC and a desk top, then this is adequate. It's ability to take samples over an hour or two suggests it's a good candidate for data logging.
What disturbs me is there is nothing I see stating the amount of RAM this has for sample storage. There is a balance between the amount of memory and the algorithms to fit the signal curve. An erratic signal with very few sample points leads to a poor and meaningless signal display.
As for buying used 'scopes, if you don't get an assurance up front that the unit has been recertified recently and well cared for, you might as burn your money.
I didn't notice. Did this come with probes? If not, forget this thing and look elsewhere.
P.S. The difference between this and the NI data logger is basically:
a. the scope takes many more samples per second, and
b. the NI unit has 12 bits (4096 parts) sampling resolution, while the scope gives only 8 bits (256 parts), which is considerably less, and
c. the NI unit costs lots more, but
d. the NI logger will sample a lot more data over a longer period of time, and
e. give you many more channels for input, analog and digital.
To my mind, as a college student, the scope will do more for you, here and now.
As an aside, the scope gives you display software. You can probably get something from NI which graphs the results of the loggers data, but will cost you something more. If you know your way around MS Excel you can use its graphs function(s) to dispaly the NI results, too.
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